The TARDIS materialises on the USS Eldridge, after the Philadelphia Experiment has gone disastrously wrong. Most of the crew are dead, the ship is disintegrating, and the Doctor soon realises that the problem comes from another dimension… As they attempt to find a way to get the ship home, the Doctor and Peri visit the distant planet Capron and meet its tyrannical ruler Osloo. But the search for a possible solution only creates increasingly dire problems. Osloo's horizons have been widened – and space and time are hers for the taking...